RU2490707C1 - Simulator of signals of resistor strain gage - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device consists of a metre bridge 1 formed by precision resisters 2, 3, 4, 5, linearising resistor 6, reference voltage source 8, differential amplifier 7, difference scheme 9, integrator 10; at that outputs of the metre bridge 1 are connected to the following inputs: differential amplifier 7; outputs of reference voltage source 8 and differential amplifier 7 are connected to inputs of difference scheme 9, output of the difference scheme 8 is connected to the integrator 10 input; output of the integrator 10 is connected to one output of offset-setting resistor 6 while the other output offset-setting resistor 6 is connected to one output of the metre bridge.

EFFECT: enlarging the range for offset voltage value of strain-measuring bridges due to automatic maintenance of offset voltage which depends only on coefficient of amplification K of the differential amplifier and voltage Uref of reference voltage source.

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Description

The simulator of the output signals of strain gauges refers to the technique of metrology for testing and certification of secondary strain gauges.

Known simulator of the output signals of strain gauges, designed for metrological verification, certification and commissioning of secondary strain gauges, containing a bridge or half bridge circuit, a set of electromagnetic relays, contact pairs of which switch one or another combination of a set of constant resistors to the arms of the measuring circuit [1]. Such a simulator has a limited set of output signal imbalance levels, is capable of simulating only static signals, has a small resource due to the presence of mechanical contacts, and does not allow automation of the process of verification and certification of secondary strain gauges.

Of the known closest in technical essence is a simulator of the output signals of strain gauges [2], the structural diagram of which is shown in figure 1. The simulator contains a simulating circuit - a measuring bridge 1, the shoulders of which are formed by resistors 2, 3, 4, 5, the first diode 6, two linearizing resistors 7, 8, and also a reference voltage source 9 with terminals 10, 11. Terminals 12, 13 of one diagonal the bridge are used to connect it to a power source 14, the findings 15, 16 of its other diagonal are informational for the secondary device. The connection point of the first terminals of the resistors 7, 8 is connected to the cathode of the diode 6, the anode of which is connected to the first terminal of the power diagonal. The second terminal of one of these resistors is connected to one of the information terminals of the bridge and one of the terminals 10 of the reference voltage source, the other terminal of which is connected to the second terminal of the other of these resistors.

The device operates as follows. Depending on the magnitude of the reference voltage Uob, the resistance of the resistors R2 or R4 of the measuring bridge changes, as a result of which an increase in the output voltage of the simulator of the output signals of the strain gauges appears.

The circuit of diode 17 and resistors 18 and 19 shown in Fig. 1 provides, on the one hand, compensation for the temperature effect of the diodes and thereby reduces the temperature error of the simulator, on the other hand, the reciprocal change in the resistances of adjacent arms of the bridge circuit from the action of the reference voltage, which leads to doubling the output signal.

The disadvantages of this simulator of the output signals of strain gages are the nonlinearity of the dependence of the output signal (unbalance voltage of the bridge) on the magnitude of the reference voltage, the temperature instability of the output signal due to the presence of non-linear elements with high temperature sensitivity (diodes) in the unbalance reference circuit, a small range of variation of the unbalance voltage of the bridge at an acceptable accuracy.

The purpose of the invention is to improve the accuracy and temperature stability of setting voltage imbalance simulator output signals of strain gauges.

This goal is achieved by the fact that in the simulator of the output signals of the strain gages, containing a measuring bridge, the conclusions of one diagonal of which are connected to the power source, and the conclusions of the other diagonal are information outputs of the simulator, a reference voltage source, a linearizing resistor, the second output of which is connected to one of the information outputs bridge, according to the invention, a differential amplifier is introduced, the inputs of which are connected to the outputs of the measuring bridge, a differential circuit, the first in od which is connected to the output of an exemplary source voltage, and the second - the differential amplifier, and an integrator whose input is connected to the output of the difference circuit, and an output coupled to a first terminal of linearizing resistor.

Figure 2 shows the structural diagram of the proposed simulator of the output signals of the strain gauges. The simulator consists of a measuring bridge 1 formed by precision resistors 2, 3, 4, 5, a linearizing resistor 6, a reference voltage source (ION) 8, a differential amplifier (DU) 7, a difference circuit 9, an integrator 10.

The device operates as follows. When a supply voltage Uп is applied to the measuring bridge 1, the output signal of the bridge 1 is formed - the unbalance voltage Uout, which is amplified by DN 7 K times (Udu = K · Uout). The difference circuit 9 subtracts the output voltage Udu of the differential amplifier 7 from the voltage Uob set by ION 8. The resulting difference ΔU = Uob-Udu goes to the integrator 10. The output voltage U and the integrator changes when there is a difference ΔU, thereby providing a change in the output through the linearizing resistor 6 voltage Uout of the measuring bridge 1 until the output voltage Udu of the differential amplifier 7 becomes equal to the voltage Uoob set by ION 8. In this case, Udu = K · Uout = Uo, whence Uout = Uo / K.

Thus, the simulator provides high accuracy, temperature stability and a wide range of setting the unbalance voltage of the measuring strain gauges by changing the structure of the simulator and eliminating non-linear elements sensitive to temperature changes from the circuit, automatically maintains the unbalance voltage Uout, which depends only on the gain K of the differential amplifier and voltage Uab of a source of exemplary voltage.

Information sources

1. Operation manual 4T2. 702.002RE. The simulator of the output signals of strain gauges exemplary IST-1. Krasnodar Plant "Tenzopribor", 1988, p.10-12.

2. Patent RU 2022363, C2, IPC 5 G05G 7/62, publ. 10/30/1994 g.

3. Patent RU 2391692, C2, IPC 5 G05B 17/00, publ. 06/10/2010

Claims (1)

A strain gage output simulator containing a measuring bridge, the terminals of one diagonal of which are connected to a power source, and the terminals of the other diagonal are information outputs of a simulator, a reference voltage source, a linearizing resistor, the second terminal of which is connected to one of the information terminals of the bridge, characterized in that it introduced a differential amplifier, the inputs of which are connected to the outputs of the measuring bridge, a difference circuit, the first input of which is connected to the output of the source sample th voltage, and the second - the differential amplifier, and an integrator whose input is connected to the output of the difference circuit, and an output coupled to a first terminal of linearizing resistor.

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